1. Field of the Invention
The present invention relates to an object, a method, or a manufacturing method. In addition, the present invention relates to a process, a machine, manufacture, or a composition of matter. In particular, one embodiment of the present invention relates to a semiconductor device, a display device, a light-emitting device, a power storage device, a storage device, a driving method thereof, or a manufacturing method thereof.
In this specification and the like, a semiconductor device generally means a device that can function by utilizing semiconductor characteristics. A transistor and a semiconductor circuit are embodiments of semiconductor devices. An arithmetic device, a memory device, an imaging device, an electro-optical device, a power generation device (e.g., a thin film solar cell and an organic thin film solar cell), and an electronic appliance each may include a semiconductor device.
2. Description of the Related Art
Non-Patent Document 1 discloses that a homologous series represented by In1−xGa1+xO3(ZnO)m (−1≦x≦1, and m is a natural number) exists. Furthermore, Non-Patent Document 1 discloses a solid solution range of a homologous series. For example, in the case of a solid solution range of a homologous series when m is 1, x is within a range from −0.33 to 0.08, and in the case of a solid solution range of a homologous series when m is 2, x is within a range from −0.68 to 0.32.
A compound represented by AB2O4(A and B are metal elements) is known as a compound having a spinel crystal structure. In addition, Non-Patent Document 1 discloses an example of InxZnyGazOw, and when x, y, and z are set so that a composition in the neighborhood of ZnGa2O4 is obtained, i.e., x, y, and z are close to 0, 1, and 2, respectively, a spinel crystal structure is formed or is likely to be mixed.
A technique in which a transistor is formed using a semiconductor material has attracted attention. The transistor is applied to a wide range of electronic devices such as an integrated circuit (IC) or an image display device (also simply referred to as a display device). As semiconductor materials applicable to the transistor, silicon-based semiconductor materials have been widely used, but oxide semiconductors have been attracting attention as alternative materials.
For example, a technique for formation of a transistor using zinc oxide or an In—Ga—Zn oxide semiconductor as an oxide semiconductor is disclosed (see Patent Documents 1 and 2).
In recent years, demand for integrated circuits in which semiconductor elements such as miniaturized transistors are integrated with high density has risen with increased performance and reductions in the size and weight of electronic appliances.